TipTo see the distribution
of photons for global illumination, you can generate a 3-dimensional
visualization map in shaded or wireframe scene views. For more information,
see
See the distribution of photons.
Photon maps are:
- Required to produce global illumination
and caustic effects. (They are not required for Final Gather.)
- A 3D representation of the accumulated
light energy at certain photon bounce points.
- Conceptually similar to shadow maps,
but they capture light instead.
- Created during the
Photon tracing stage.
- Used by the material shaders for those
surfaces that participate in global illumination at render time
to calculate the contribution of Global illumination and caustics.
(This is added to any contribution provided by local (direct) illumination
in the scene.)
GI photon maps vs. caustic
photon maps
Photons that are specularly
reflected or refracted are stored in the caustic photon map; all
other photons are stored in the global illumination map.
As the Shinyness parameter
of the photon shader attached to an object increases, specular highlights
become smaller and the likelihood of specular reflection increases.
In this case, more photons migrate from the global illumination
map into the caustic photon map, decreasing the density of the global
illumination map. (Similar considerations apply to the Translucence parameter,
but in the opposite direction: when Translucence is increased, photons
migrate from the caustic photon map into the global illumination photon
map.)
